Optical transmitter-receiver module and electronic device using the same

ABSTRACT

In an optical transmitter-receiver module for performing optical transmission and reception by using a single-core optical fiber, a light-tight partition plate unit  506  for separation between an optical path of a transmission signal light and an optical path of a reception signal light is held between a jack section  508  for detachably holding an optical plug  240  and a light emitting/receiving unit  505  which has an LED  514  and a PD  515  positioned and fixed in place and molded in one piece. The LED  514  is located at a larger a distance in a direction of optical axis from the optical fiber than the PD  515  is. The partition plate unit  506  is urged toward the optical fiber by springs.

BACKGROUND OF THE INVENTION

The present invention relates to an optical transmitter-receiver moduleand an electronic device for use in a single-core bidirectional opticaltransmitter-receiver system capable of performing transmission andreception with a single-core optical fiber. The present inventionrelates, in particular, to a digital communication system, which is ableto perform high-speed transmission, such as IEEE1394 (Institute ofElectrical and Electronic Engineers 1394) and USB (Universal Serial Bus)2.0.

Conventionally, as a first optical transmitter-receiver module, there isa one as described in Japanese Patent Laid-Open Publication No.2001-116961. In this optical transmitter-receiver module, full-duplexcommunications are achieved by reducing electric crosstalk by employinga shield plate while reducing optical crosstalk by employing alight-tight partition plate that abuts against the end surface of theoptical fiber so as to separate the light-emitting device and thelight-receiving device from each other.

FIG. 35A and FIG. 36A are plan views of a partition plate 1019, whileFIG. 35B and FIG. 36B are side views showing the positional relationshipof the partition plate 1019 with respect to an optical plug 1030. Withregard to this first optical transmitter-receiver module, FIGS. 35A and35B shows a state in which the optical plug 1030 provided internallywith a single-core optical fiber 1032 is partway inserted in an opticaltransmitter-receiver module (overall view is not shown) and startscoming in contact with the partition plate 1019. FIGS. 36A and 36B showa state in which the optical plug 1030 is completely inserted in theoptical transmitter-receiver module and fully put in contact with thepartition plate 1019.

FIG. 37A shows a side view of an essential part of an optical cable,which has the plug 1030 and constitutes an optical transmitter-receiversystem with the aforementioned optical transmitter-receiver module,while FIG. 37B shows a rear view of the optical cable that has theoptical plug 1030. As shown in FIGS. 37A and 37B, the optical plug 1030(including the optical fiber) is provided at each end portion (only oneend portion is shown) of the optical cable, and a front end of theoptical plug 1030, which includes a tip of the optical fiber, has aninclined surface 1030 a inclined forward in the lengthwise direction ofthe optical fiber (i.e., toward the other optical transmitter-receivermodule side not shown). Moreover, the optical plug 1030 is provided witha anti-rotation key 1031 extended in the horizontal direction, and theoptical transmitter-receiver module is internally provided with a keyway(not shown) that cooperates with the key 1031, for preventing possiblechanges in the optical input and characteristics in accordance with therotation of the optical plug 1030.

Moreover, as a second conventional optical transmitter-receiver module,there is a one as described in Japanese Patent Laid-Open Publication No.2001-147349. As shown in FIG. 38, this second opticaltransmitter-receiver module employs a partition plate 1111 similar tothat of the aforementioned first conventional opticaltransmitter-receiver module that has an optical system employing aFoucault prism 1104. According to this, in the second opticaltransmitter-receiver module, the end surface of the optical fiber 1102of the optical plug 1101 abuts against the partition plate 1111, and alight-emitting element 1103 and a light-receiving element 1105 aremolded or encapsulated with a molding resin 1106. Lens portions 1106 aand 1106 b are integrally formed in the plastic molding stage of themolding resin.

In the aforementioned first conventional optical transmitter-receivermodule, the optical plug 1030 has the anti-rotation key 1031. Therefore,the optical plug 1030 cannot be inserted into the opticaltransmitter-receiver module unless the key 1031 is aligned with thekeyway of the optical transmitter-receiver module when fitting theoptical plug 1030, and this disadvantageously causes inconvenience tothe user. However, if the anti-rotation key 1031 of the optical plug1030 is removed to improve the convenience at the time of insertion ofthe optical plug, then the optical plug 1030 becomes rotatable.Therefore, if the optical plug 1030 rotates with an optical fiber endsurface 1030 a being in contact with the partition plate 1019, thenthere occurs a problem that the inclined end surface 1030 a of theoptical fiber and/or the partition plate 1019 is damaged.

Moreover, the second conventional optical transmitter-receiver module,which employs the Foucault prism optical system having the partitionplate 1111 similar to that of the first conventional opticaltransmitter-receiver module, has the structure in which the partitionplate 1111 abuts against the end surface of the optical fiber 1102.Therefore, similarly to the first conventional opticaltransmitter-receiver module, there occurs a problem that the end surfaceof the optical fiber 1102 and/or the partition plate 1111 is damaged.Furthermore, the light-emitting element 1103 and the light-receivingelement 1105 are mounted on an identical substrate 1109 in this secondoptical transmitter-receiver module, but the optical positions of thelight-emitting element 1103 and the light-receiving element 1105 are notoptimized with regard to the optical system that has the partition plate1111.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide an opticaltransmitter-receiver module and an electronic device using the same,which module is able to perform high-quality optical transmission byfull-duplex communication scheme by using a light-tight partition plateand able to prevent the optical fiber end surface and the partitionplate from being damaged even if the inserted optical plug is rotated inthe module.

In order to accomplish the above object, the present invention providesan optical transmitter-receiver module having a light-emitting elementfor emitting transmission signal light and a light-receiving element forreceiving reception signal light, said module being able to perform bothtransmission of the transmission signal light and reception of thereception signal light by means of a single-core optical fiber, saidmodule comprising:

a jack section for detachably holding an optical plug provided at an endportion of the optical fiber;

a light emitting/receiving unit having the light-emitting element andlight-receiving element positioned and fixed in place and molded in onepiece; and

a light-tight partition plate unit for separating an optical path of thetransmission signal light and an optical path of the reception signallight from each other, said light-tight partition plate being arrangedso as to be held between the jack section and the lightemitting/receiving unit,

the light-tight partition plate unit having spring means for urging thisunit toward the optical fiber.

According to the optical transmitter-receiver module of the aboveconstruction, by arranging the light-tight partition plate unit forseparation between the optical path of the transmission signal light andthe optical path of the reception signal light so that the plate is heldbetween the jack section and the light emitting/receiving unit, thecoupling of the transmission signal light directly with thelight-receiving element is restrained, so that high-quality opticaltransmission by the full-duplex communication method is achieved.Further, because the partition plate unit is always urged toward theoptical fiber by the spring means, the positional relation between theend surface of the optical plug and the partition plate unit is keptconstant. Therefore, high-quality optical transmission by thefull-duplex communication scheme can be performed, and the optical fiberend surface and the partition plate are prevented from being damagedeven if the inserted optical plug is rotated in the module.

In one embodiment, the partition plate unit has a partition plate forseparating an optical path of the transmission signal light and anoptical path of the reception signal light from each other, aresin-molded piece having an engagement surface with which an endsurface of the optical plug comes in contact when inserted in the jacksection, and the spring means urging the engagement surface of theresin-molded piece toward the optical plug. Also, the module furthercomprises a retaining portion for retaining the partition plate unitmovably in a direction of optical axis of the optical fiber.

In this embodiment, the partition plate unit, in which the partitionplate, the resin-molded piece and the spring means are unitized with oneanother, is retained movably in the direction of the optical axis of theoptical fiber by the retaining portion. Therefore, even if variationsoccur in the length in the direction of the optical axis of the opticalfiber of the optical plug, the partition plate unit is moved by thespring means so that the positional relation between the end surface ofthe optical plug and the partition plate becomes constant.

In one embodiment, the spring means of the partition plate unit areprovided in at least two places located on a plane approximatelyperpendicular to the optical axis of the fiber and on a diagonal line ofthe resin molding.

With this arrangement, the partition plate unit can stably be moved bybeing urged in the direction of the optical axis of the optical fiber bya necessary minimum number of spring means without being inclined, andthe reduction in size and the simplification of the partition plate unitcan be achieved.

In one embodiment, the partition plate and resin-molded piece of thepartition plate unit are formed into one piece by insert molding.

This arrangement enables an easy assembling of the module, in comparisonwith a case of combining small separate members, which leads to adifficult assembling. Also, the required dimensional accuracy can easilybe obtained so that high-quality optical transmission by the full-duplexcommunication method can be achieved. In addition, the partition plateunit can be downsized.

In one embodiment, the partition plate of the partition plate unit has aplanar opposed surface that faces an end surface of the optical fiberwith a gap therebetween when the optical plug is placed in positionwithin the module.

With this arrangement, dimensional accuracy of the planar opposedsurface with respect to the optical fiber end surface can easily beobtained. Also, the partition plate having the planar surface can beprocessed at lower cost than when having a curved opposed surface.

In one embodiment, an optical absorption layer is provided on theopposite surface of the partition plate.

With this arrangement, the signal light emitted from the end surface ofthe optical fiber is prevented from being reflected by the opposedsurface of the partition plate, to which the emitted signal light firstgets.

In one embodiment, the engagement surface of the resin-molded piececomes in contact with a peripheral edge portion of the end surface ofthe optical plug. Therefore, the positional adjustment of the endsurface of the optical plug can easily be achieved without damaging theoptical fiber end surface.

In one embodiment, the partition plate is sized such that a distance ina direction of optical axis from said end surface of the optical fiberto an end opposite from the optical fiber of the partition plate isgreater than distances in a direction of optical axis from said endsurface of the optical fiber to each of a bottom of a transmission lensprovided on emission side of the light-emitting element and a bottom ofa reception lens provided on incident side of the light-receivingelement.

With this arrangement, the transmission signal light (includingreflection light) emitted from the light-emitting element is reliablyprevented from being incident on the light-receiving element, so thatthe optical crosstalk can effectively be reduced.

By employing the above-mentioned optical transmitter-receiver module,there can be provided electronic equipment such as an informationdomestic appliance capable of performing optical transmission by ahigh-quality full-duplex communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not intendedto limit the present invention, and wherein:

FIG. 1 is a flowchart showing the manufacturing method of an opticaltransmitter-receiver module according to one embodiment of thisinvention;

FIG. 2 is a top view of the above optical transmitter-receiver module;

FIG. 3 is a view of the above optical transmitter-receiver module seenfrom the direction of a plug insertion hole;

FIG. 4 is a side view of the above optical transmitter-receiver module;

FIG. 5 is a sectional view taken along line V—V of FIG. 4;

FIG. 6 is an enlarged sectional view showing an optical system in theabove optical transmitter-receiver module;

FIG. 7 is a flowchart for explaining the manufacturing process steps fora light-emitting device;

FIG. 8 is a flowchart for explaining the manufacturing process steps fora light-receiving device;

FIG. 9A is a top view of the above light-emitting device, and FIG. 9B isa side view of the above light-emitting device;

FIG. 10A is a top view of the above light-receiving device, and FIG. 10Bis a side view of the above light-receiving device;

FIG. 11 is a flowchart for explaining the manufacturing process stepsfor a light emitting/receiving unit;

FIG. 12A is a front view of a light-emitting device on which an uppershield plate and a lower shield plate are mounted, FIG. 12B is a rearview of the above light-emitting device, and FIG. 12C is a side view ofthe light-emitting device of FIG. 12A as viewed from the right-handside;

FIG. 13A is a front view of the upper shield plate, and FIG. 13B is aside view of the upper shield plate;

FIG. 14A is a front view of the lower shield plate, and FIG. 14B is aside view of the lower shield plate;

FIG. 15A is a front view of a light-receiving device on which an uppershield plate and a lower shield plate are mounted, FIG. 15B is a rearview of the above light-receiving device, and FIG. 15C is a side view ofthe light-receiving device of FIG. 15A as viewed from the right-handside;

FIG. 16A is a front view of the upper shield plate, and FIG. 16B is aside view of the upper shield plate;

FIG. 17A is a front view of the lower shield plate, and FIG. 17B is aside view of the lower shield plate;

FIG. 18A is a front view of a light emitting/receiving unit integratedby secondary injection resin molding, FIG. 18B is a sectional view takenalong line XVIIIb—XVIIIb of FIG. 18A, FIG. 18C is a side view of theabove light emitting/receiving unit, and FIG. 18D is a rear view of theabove light emitting/receiving unit;

FIG. 19A is a front view of a transmission prism lens, FIG. 19B is aview seen from the upper side of the transmission prism lens of FIG.19A, and FIG. 19C is a side view seen from the right-hand side of thetransmission prism lens of FIG. 19A;

FIG. 20A is a front view of a reception prism lens, FIG. 20B is a viewseen from the upper side of the reception prism lens of FIG. 20A, andFIG. 20C is a side view seen from the right-hand side of the receptionprism lens of FIG. 20A;

FIG. 21A is a front view of a light emitting/receiving unit in which theabove transmission prism lens and the reception prism lens are inserted,FIG. 21B is a sectional view taken along line XXIb—XXIb of FIG. 21A,FIG. 21C is a side view of the light emitting/receiving unit, and FIG.21D is a rear view of the light emitting/receiving unit;

FIG. 22A is a side view of a jack section, FIG. 22B is a side view of apartition plate unit, FIG. 22C is a side view of a lightemitting/receiving unit, and FIG. 22D is a view of the jack section ofFIG. 22A seen from the lower side;

FIG. 23 is a sectional view of an optical transmitter-receiver module ina state in which an optical plug is inserted in a plug insertion hole;

FIG. 24 is a flowchart for explaining a method of manufacturing theabove partition plate unit;

FIG. 25 is a side view of a partition plate unit;

FIG. 26 is a front view of the above partition plate unit;

FIG. 27 is a side view of the partition plate unit of FIG. 26 seen fromthe right-hand side;

FIG. 28 is a sectional view taken along line XXVIII—XXVIII of FIG. 26;

FIG. 29 is a side view of an optical cable;

FIG. 30 is a sectional view showing a state in which the front end of anoptical plug is fit in a hole of an engagement portion of the partitionplate unit;

FIG. 31 is a sectional view of an optical transmitter-receiver module inwhich an optical plug is inserted in a jack section;

FIG. 32A is a plan view of a light-emitting element drive circuit board,and FIG. 32B is a plan view of a light-receiving element amplificationelectric circuit board;

FIG. 33 is a block diagram schematically showing an opticaltransmitter-receiver system in which the optical transmitter-receivermodule of this invention is employed;

FIG. 34 is a block diagram schematically showing another opticaltransmitter-receiver system in which the optical transmitter-receivermodule of this invention is employed;

FIG. 35A is a plan view of a partition plate of the first conventionaloptical transmitter-receiver module, and FIG. 35B is a side view showingthe positional relationship of the partition plate with respect to anoptical plug;

FIG. 36A is a plan view of the partition plate of the above opticaltransmitter-receiver module, and FIG. 36B is a side view showing thepositional relationship of the partition plate with respect to theoptical plug;

FIG. 37A is a side view showing an essential part of an optical cablethat has an optical plug and constitutes an optical transmitter-receiversystem with the above optical transmitter-receiver module, and FIG. 37Bis a rear view of the optical cable that has the optical plug; and

FIG. 38 is a sectional view of the second conventional opticaltransmitter-receiver module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The optical transmitter-receiver module and electronic equipment of thisinvention will be described in detail below on the basis of theembodiments thereof shown in the drawings.

In explaining an embodiment of this invention, the outline of a methodof manufacturing the optical transmitter-receiver module of thisinvention will be first described, and the construction of the opticaltransmitter-receiver module and the details of the manufacturing methodwill be subsequently described.

FIG. 1 is a flowchart showing the manufacturing method for the opticaltransmitter-receiver module of this embodiment. The opticaltransmitter-receiver module of this embodiment is manufactured accordingto the flowchart of FIG. 1.

First, in step S1, a light-emitting device is manufactured byencapsulating a light-emitting element by transfer molding.

Next, in step S2, a light-receiving device is manufactured byencapsulating a light-receiving element by transfer molding.

Next, in step S3, the light-emitting device and the light-receivingdevice are integrated with each other by being subjected to secondaryinjection resin molding for positioning and fixation of the devices.

Next, in step S4, a light emitting/receiving unit is formed by insertinga transmission prism lens as an optical element and a reception prismlens as an optical element to combine the lenses with the integrateddevices by tertiary injection resin molding.

Next, in step S5, an assembly 1 is manufactured by combining the lightemitting/receiving unit with a partition plate unit.

Next, in step S6, an assembly 2 is manufactured by combining theassembly 1 with a jack section having a plug insertion hole and anengagement retaining portion for enabling the attaching and detaching ofan optical fiber cable provided with an optical plug for optical signaltransmission.

Next, in step S7, an assembly 3 is manufactured by combining theassembly 2 with a transmission drive electric circuit board as alight-emitting element drive circuit board and a reception amplificationelectric circuit board as a light-receiving element processing circuitboard.

Further, in step S8, an optical transmitter-receiver module ismanufactured by combining the assembly 3 with an armor shield.

FIGS. 2 through 4 show the external views of the opticaltransmitter-receiver module of the embodiment. FIG. 2 is a top view ofthe optical transmitter-receiver module. FIG. 3 is a view of the opticaltransmitter-receiver module seen from the direction of the pluginsertion hole. FIG. 4 is a side view of the opticaltransmitter-receiver module. In FIGS. 2 through 4 are shown a lightemitting/receiving unit 21, a jack section 22, an armor shield 23, aplug insertion hole 24, external input/output terminals 25 andrectangular holes 26 for retaining shield plates.

FIG. 6 is an enlarged sectional view showing an optical system in theoptical transmitter-receiver module. The optical system arrangement ofthe optical transmitter-receiver module of this embodiment will bedescribed first. In the embodiment, a light-emitting diode (hereinafterreferred to as an LED) 34 is employed as a light-emitting element, and aphotodiode (hereinafter referred to as a PD) 37 is employed as alight-receiving element.

As shown in FIG. 6, a partition plate 31 is arranged in front of anoptical plug 30 that includes an optical fiber 44. A prism lens, whichis an optical element, is divided into two parts of a transmission prismlens 32 and a reception prism lens 35, and the partition plate 31 isarranged in the boundary therebetween. This partition plate 31 has athickness of 50 μm, and an interval between the transmission prism lens32 and the reception prism lens 35 between which the partition plate 31is inserted is set to 100 μm. The partition plate 31 is arranged in acenter position (in a plane that includes the optical axis of theoptical fiber) of the optical plug 30. The above arrangement is to setthe projection area of the front end of the optical plug 30 at 50% onthe transmission side and 50% on the reception side.

According to this embodiment, the LED 34 is encapsulated with a moldingresin 33 by the transfer molding method or the like, and a transmissionlens 39 is provided by the molding resin used at this time. Likewise,the PD 37 is encapsulated with a molding resin 36 by the transfermolding method or the like, and a reception lens 41 is provided by themolding resin used at this time. Transmission light from the LED 34 iscollimated by a condenser lens 38 on the transmission prism lens 32 viathe transmission lens 39, refracted by a prism portion 42 and thereaftercoupled to an optical fiber 44. On the other hand, due to the partitionplate 31, half the reception light emitted from the optical fiber 44 isrefracted by the prism portion 43 of the reception prism lens 35,thereafter condensed by a condenser lens 40 and coupled with thereception PD 37 via the reception lens 41 of the molding resin 36. Asdescribed above, by inserting the partition plate 31, the transmissionprism lens 32 and the reception prism lens 35 between the LED 34 and PD37 and the optical fiber 44, it is enabled to perform transmission andreception, i.e., full-duplex communications by means of one opticalfiber 44.

In this embodiment, the LED 34 is arranged in a position farther thanthe PD 37 with respect to the front ends of the optical plug 30 and theoptical fiber 44. In this case, a difference between a distance from theoptical plug 30 to the light-emitting surface of the LED 34 and adistance from the optical plug 30 to the light-receiving surface of thePD 37 is 1.3 mm. Further, the condenser lens 38 of the transmissionprism 32 is arranged in a position farther than the condenser lens 40 ofthe reception prism lens 35 with respect to the front end of the opticalplug 30. A difference between a distance from the front end of theoptical fiber 44 to the condenser lens 38 and a distance from the frontend of the optical fiber 44 to the condenser lens 40 is 1 mm. In thisembodiment, the partition plate 31 is inserted between thelight-emitting device in which the LED 34 is molded by transfer moldingand the light-receiving device in which the PD 37 is molded by transfermolding. Therefore, it is impossible to arrange both the LED 34 and thePD 37 at a distance of less than 50 μm from the center position of theoptical plug 30.

With regard to the optical system arrangement on the transmission side,the radiation light intensity of the LED 34 decreases with a peak at thecenter of the light-emitting portion as the angle increases, and thetransmission efficiency becomes higher when the coupling of the lightwith the optical fiber of the optical plug 30 is attained with lessbending of the ray of light at the prism portion 42 of the transmissionprism lens 32. Therefore, the efficiency increases as the angle madebetween the light-emitting direction of the LED 34 and the direction ofthe optical axis of the optical fiber of the optical plug 30 decreases.For the above reasons, it may be conceivable to adopt a method ofdecreasing the angle between the LED 34 and the optical plug 30 byputting the LED 34 away from the front end of the optical plug 30.However, for the sake of downsizing the optical transmitter-receivermodule, to place the LED 34 and the PD 37 away from the optical plug 30becomes a negative factor due to the increase in size of the opticalsystem. For the above reasons, in this embodiment, the LED 34 isarranged so that the distance from the front end of the optical plug 30to the light-emitting portion of the LED 34 is about 4.75 mm. In thiscase, it is difficult to make the light emitted from the LED 34 whollybecome parallel light by the transmission lens 39. Therefore, it isdesirable to reduce the interval between the transmission lens 39integrally molded by transfer molding and the condenser lens 38 of thetransmission prism lens 32, thereby making fast incidence of light onthe condenser lens 38. In this embodiment, the interval between thetransmission lens 39 and the condenser lens 38 is set at 50 μm.

On the other hand, with regard to the optical system arrangement on thereception side, because the front end of the optical fiber of theoptical plug 30 has a spherical surface, and therefore, the lightemitted from the front end of the optical fiber tends to be concentratedtoward the center, the reception efficiency is increased by arrangingthe prism portion 43 of the reception prism lens 35 in a position nearthe front end of the optical fiber so that the light is bent toward thereception side by the prism portion 43 of the reception prism lens 35before the light strikes the partition plate 31, and then collimated bymeans of the condenser lens 40 of the reception prism lens 35 for thecoupling with the PD 37 through the reception lens 41.

For the above reasons, the LED 34 is arranged in the position fartherthan the PD 37 with respect to the front end of the optical plug 30.Furthermore, the condenser lens 38 of the transmission prism 32 is alsoarranged in the position farther than the condenser lens 40 of thereception prism lens 35 with respect to the front end of the opticalplug.

As described above, the optical positions of the LED 34 and the PD 37are optimized. According to the optical simulation results of theoptical system arrangement of this embodiment, the transmissionefficiency of this optical system was 21.3%, and the receptionefficiency was 31.2%, meaning that high transmission efficiency andreception efficiency were obtained.

The process steps of manufacturing the optical transmitter-receivermodule of this embodiment will be described below.

FIG. 7 is a flowchart for explaining the process steps of manufacturinga light-emitting device. FIG. 9A shows a top view of the light-emittingdevice. FIG. 9B shows a side view of the light-emitting device. As thelight-emitting device of this embodiment, an LED (light-emitting diode)51 (shown in FIG. 9A) is employed.

First, in step S11, the LED 51 of the light-emitting element isdie-bonded onto a lead frame 50 (shown in FIG. 9A) with silver paste,conductive resin, indium or the like. The lead frame 50 is formed bycutting or etching a metal plate, such as a copper plate or an ironplate, plated with silver. One electrical connection of the LED 51 isprovided in a prescribed position on the lead frame 50 using the silverpaste, conductive resin, indium or the like, whereby the LED is fixed.

Next, in step S12, the other electrical connection of the LED 51 isprovided in a prescribed position on the lead frame 50 by wire bondingwith a gold wire or an aluminum wire 54 (shown in FIG. 9A).

Subsequently, in step 13, the resulting assembly is set in a metal moldand encapsulated with a molding resin 53 (shown in FIGS. 9A and 9B) bytransfer molding.

As the resin used in the process steps of manufacturing thislight-emitting device, an epoxy-based transparent material is used. Atthis time, by integrally forming a lens portion 52 (shown in FIGS. 9Aand 9B) that has a spherical or aspherical surface, using the moldingresin, in a direction inclined with respect to the light-emittingelement, the efficiency of coupling of the light-emitting element withthe optical fiber during transmission can be improved.

FIG. 8 is a flowchart for explaining the process steps of manufacturinga light-receiving device. FIG. 10A is a top view of the light-receivingdevice. FIG. 10B is a side view of the light-receiving device. As thelight-receiving device of this embodiment, a PD (photodiode) 71 (shownin FIG. 10A) is employed.

First, in step S21, the PD 71 and a first-stage amplification IC(hereinafter referred to as a preamplifier) 75 (shown in FIG. 10A) aredie-bonded onto a lead frame 70 (shown in FIG. 10A) using silver paste,conductive resin, indium or the like, similarly to the manufacturingflow of the light-emitting device. The lead frame 70 is formed bycutting or etching a metal plate, such as a copper plate or an ironplate, plated with silver. The electrical connection of the PD 71 at itsbottom side and the grounding connection of the preamplifier areprovided in a prescribed position on the lead frame using the silverpaste, conductive resin, indium or the like, whereby the PD and thepreamplifier are fixed.

Next, in step S22, the light-receiving surface side of the PD 71 and thepreamplifier 75 are connected to prescribed positions on the lead frame70 by wire bonding using a gold wire or an aluminum wire 74 (shown inFIG. 10A). In this case, the light-receiving surface side electrode ofthe PD and the PD connection pad of the preamplifier are electricallyconnected directly to each other by wire bonding using a wire 76 inorder to prevent the capacitance from increasing.

Subsequently, in step S23, the resulting assembly is set in a metal moldand encapsulated with a molding resin 73 (shown in FIGS. 10A and 10B) bytransfer molding.

As the resin used in the process of manufacturing this light-receivingdevice, an epoxy-based transparent material is used. At this time, byintegrally forming a lens portion 72 (shown in FIGS. 10A and 10B) thathas a spherical or aspherical surface, using the molding resin, in adirection inclined with respect to the light-receiving element, theefficiency of coupling of the light-receiving element with the opticalfiber during reception can be improved. Although the PD and thepreamplifier are constructed of individual chips in this embodiment, itis acceptable to use a single-chip construction of a photoelectric IC(OPIC, OEIC) or the like.

FIG. 11 is a flowchart for explaining the process steps of manufacturinga light emitting/receiving unit. First, a shield plate is mounted on thelight-emitting device in step S31, and a shield plate is mounted on thelight-receiving device in step S32.

Next, in step S33, the light-emitting device and the light-receivingdevice, on each of which the shield plate has been mounted, areintegrated with each other into a unit by secondary injection resinmolding.

Next, in step S34, prism lenses are inserted in the unit obtained by thesecondary injection resin molding.

Next, in step S35, tertiary injection resin molding is performed to forma lens fixing portion 195, which will be described later, to fix thelens.

The steps of mounting the shield plate on the light-emitting device willbe described in more detail next.

FIG. 12A through FIG. 12C are views of an assembly in which an uppershield plate 93 and a lower shield plate 94 are mounted on thelight-emitting device 91 so as to cover the device. FIG. 12A is a frontview of the assembly seen from the direction of the lens portion 92integrally molded with a molding resin. FIG. 12B is a view of theassembly seen from the opposite side from the lens portion 92. FIG. 12Cis a side view of the assembly seen from the right-hand side of FIG.12A. FIG. 13A is a front view of the upper shield plate 93. FIG. 13B isa side view of the upper shield plate 93. FIG. 14A is a front view ofthe lower shield plate 94. FIG. 14B is a side view of the lower shieldplate 94.

In order to restrain the influence of electromagnetic noises, which aregenerated from the LED and incident on the adjacent light-receivingdevice and the amplification circuit for the light-receiving device, thelight-emitting device 91 shown in FIGS. 12A through 12C is shielded witha structure in which the device is covered with a metal plate of iron,copper or the like as a means for removing electromagnetic noisesradiated to the outside from the light-emitting device, wires and leadterminals when the light-emitting element is subjected to high-speedswitching.

In order to easily perform the assembling, this shield plate provided bythe metal plate of iron, copper or the like is divided into two parts ofthe upper shield plate 93 and the lower shield plate 94. The uppershield plate 93 has a structure for covering the upper portions otherthan the lens portion 92 and is provided with a hole 100 (shown in FIG.13A) for avoiding the lens portion 92. The upper shield plate 93 iselectrically connected to the ground by means of connection terminals95, and the lower shield plate 94 is electrically connected to theground by means of connection terminals 96, restraining the entry ofelectromagnetic noises. The connection terminals 95 and 96 of the uppershield plate 93 and the lower shield plate 94 are extended in adirection in which the lead terminals 99 of the light-emitting device 91are extended for the provision of a structure capable of providingcontinuity to the grounding terminals included in the lead terminals 99.Thus, the connection terminals 95 and 96 are electrically connected tothe ground for the restraint of the entry of electromagnetic noises. Theelectrical connection of the connection terminals 95 and 96 of the uppershield plate 93 and the lower shield plate 94 with the groundingterminals (located on both sides in FIG. 12A) in the lead terminals 99of the light-emitting device 91 are provided by welding (or soldering)at connecting portions 101, and the upper shield plate 93 and the lowershield plate 94 are positioned and fixed.

As measures for positioning and fixing the upper shield plate 93 and thelower shield plate 94, a structure for preventing the upper shield plate93 from being displaced in the upward, downward, rightward and leftwarddirections as shown in FIG. 12A is provided by making the hole 100 ofthe upper shield plate 93 for avoiding the lens portion 92 of thelight-emitting device 91 have a hole diameter slightly greater than thediameter of the lens portion 92. In this embodiment, the hole 100 has adiameter of the lens portion diameter plus 0.1 mm. Further, by providingthe connection terminals 95 and 96 of the upper shield plate 93 and thelower shield plate 94 with sectionally U-shaped portions 97 and 98 asthe positioning and fixing means, reliable positioning and fixation areachieved by sideways holding the grounding terminals (located on bothsides in FIGS. 12A and 12B) of the lead terminals 99 of thelight-emitting device 91. Moreover, the upper shield plate 93 and thelower shield plate 94 not only restrain the radiation of electromagneticnoises but also restrain the unnecessary light emission from the deviceportions other than the lens portion 92.

The process of mounting the shield plate on the light-receiving devicewill be described next.

FIG. 15A through FIG. 15C are views of an assembly in which an uppershield plate 113 and a lower shield plate 114 are mounted on alight-receiving device 111 so as to cover the device. FIG. 15A is afront view of the assembly seen from the direction of a lens portion 112integrally formed by a molding resin. FIG. 15B is a view of the assemblyseen from the opposite side from the lens portion. FIG. 15C is a sideview of the assembly seen from the right-hand side of FIG. 15A. FIG. 16Ais a front view of the upper shield plate 113. FIG. 16B is a side viewof the upper shield plate 113. FIG. 17A is a front view of the lowershield plate 114. FIG. 17B is a side view of the lower shield plate 114.

In order to restrain the influence of electromagnetic noises from theoutside, such as external noises from the adjacent light-emitting deviceand the electric circuit for driving the light-emitting device, thelight-receiving device 111 shown in FIGS. 15A through 15C is shieldedwith a structure in which the device is covered with a metal plate ofiron, copper or the like as a noise removing means.

In order to easily perform the assembling, this shield plate provided bythe metal plate of iron, copper or the like is divided into two parts ofthe upper shield plate 113 and the lower shield plate 114. The uppershield plate 113 has a structure for covering the device upper portionsother than the lens portion 112 and is provided with a hole 120 (shownin FIG. 16A) for avoiding the lens portion 112. The upper shield plate113 is electrically connected to the ground by means of a connectionterminal 115, and the lower shield plate 114 is electrically connectedto the ground by means of a connection terminal 116, restraining theentry of electromagnetic noises. The connection terminals 115 and 116 ofthe upper shield plate 113 and the lower shield plate 114 are extendedin a direction in which the lead terminals 119 of the light-receivingdevice 111 are extended for the provision of a structure capable ofproviding continuity to a grounding terminal (the second one from theright-hand side in FIG. 15A) included in the lead terminals 119. Thus,the connection terminals 115 and 116 are electrically connected to theground for the restraint of the entry of electromagnetic noises. Theelectrical connection of the connection terminals 115 and 116 of theupper shield plate 113 and the lower shield plate 114 with the groundingterminal (the second one from the right-hand side in FIG. 15A) in thelead terminals 119 of the light-receiving device 111 are provided bywelding (or soldering) at a connecting portion 121, and the upper shieldplate 113 and the lower shield plate 114 are positioned and fixed.

As means of positioning and fixing the upper shield plate 113 and thelower shield plate 114, a structure for preventing the upper shieldplate 113 from being displaced in the upward, downward, rightward andleftward directions as shown in FIG. 15A is provided by making the hole120 of the upper shield plate 113 for avoiding the lens portion 112 ofthe light-receiving device 111 have a hole diameter slightly greaterthan the diameter of the lens portion 112. In this embodiment, the hole120 has a diameter of the diameter of the lens portion 112 plus 0.1 mm.Further, by providing the connection terminals 115 and 116 of the uppershield plate 113 and the lower shield plate 114 with sectionallyU-shaped portions 117 and 118 as the positioning and fixing means,reliable positioning and fixation are achieved by sideways holding thegrounding terminal in the lead terminals 119 of the light-receivingdevice. Moreover, the upper shield plate 113 and the lower shield plate114 not only restrain the radiation of electromagnetic noises but alsorestrain the incidence of unnecessary light from the device portionsother than the lens portion 112.

The process of integrating the light-emitting device and thelight-receiving device, on which the shield plates are mounted, bysecondary injection resin molding will be described next.

FIG. 18A is a front view of the light emitting/receiving unit integratedby the secondary injection resin molding. FIG. 18B is a sectional viewtaken along line XVIIIb—XVIIIb of FIG. 18A. FIG. 18C is a side view ofthe light emitting/receiving unit. FIG. 18D is a rear view of the lightemitting/receiving unit.

As shown in FIGS. 18A through 18D, the light-emitting device 131 withthe welded shield plates 138 and 139 and the light-receiving device 132with the welded shield plates 140 and 141 are positioned and fixed, withthe lead frame of the light-emitting device 131 and the lead frame ofthe light-receiving device 132 arranged so as to extend to the mutuallyopposite sides. By arranging the light-emitting device 131 and thelight-receiving device 132 such that their sides opposite from the leadterminals 133, 134 confront each other, an interval or spacing betweenthe lead terminals 133 of the light-emitting device 131 and the leadterminals 134 of the light-receiving device 132 can be made large, sothat the influence of the electromagnetic noises from the light-emittingdevice 131 on the light-receiving device 132 can be restrained.Moreover, for the reason that the influence of electromagnetic noisesdue to electromagnetic induction between the lead terminals of thelight-emitting device and the lead terminals of the light-receivingdevice is considered to be large in the adjacent arrangement, theinfluence of electromagnetic noises can be made smaller with theaforementioned spaced arrangement.

The positioning and fixing means of the light-emitting device 131 andthe light-receiving device 132 are provided by the secondary injectionresin molding on the basis of positioning pin holes 136 and 137 of thelead frames of the light-emitting device 131 and the light-receivingdevice 132 with an injection molding resin 135. In this secondaryinjection resin molding stage, boss pin holes 142 and 143 (shown in FIG.18A) to be used as a positioning means for the prism lenses that serveas an optical element for transmission and an optical element forreception, described later, are formed at the same time.

The process of inserting the prism lenses into the lightemitting/receiving unit integrated by the secondary injection resinmolding will be described next.

The prism lenses to be inserted will be described first. FIG. 19A is afront view of a transmission prism lens. FIG. 19B is a side view seenfrom the upper side of the transmission prism lens of FIG. 19A. FIG. 19Cis a side view seen from the right-hand side of the transmission prismlens of FIG. 19A.

In this embodiment, the transmission prism lens 161 shown in FIGS. 19Athrough 19C is employed as an optical element for transmission. Thetransmission prism lens 161 has a structure in which a prism portion 162and a condenser lens portion 163 are combined into one piece. Thetransmission prism lens 161 is formed by the injection molding method orthe like, and it is desirable to select a material having excellentweather resistance for the prism lens. For example, acrylic, PMMA(polymethyl methacrylate) or the like can be employed. The transmissionprism lens 161 is provided with boss pins 164 that are integrally formedin the injection molding stage as a positioning means for the secondinjection mold in a portion that has no relation to the optics.Moreover, by providing a satin finish to the surfaces 165 and 166 of thetransmission prism lens 161, which do not contribute to the optics, sothat the unnecessary light emission and reflection of the emission lightfrom the optical fiber are restrained.

FIG. 20A is a front view of the reception prism lens. FIG. 20B is a sideview seen from the upper side of the reception prism lens of FIG. 20A.FIG. 20C is a side view seen from the right-hand side of the receptionprism lens of FIG. 20A.

In this embodiment, the reception prism lens 171 shown in FIGS. 20Athrough 20C is employed as an optical element for reception. Thereception prism lens 171 has a structure in which a prism portion 172and a condenser lens portion 173 are integrated with each other. Thereception prism lens 171 is also formed by the injection molding methodor the like similarly to the transmission prism lens 161, and it isdesirable to select a material of excellent weather resistance for theprism lens. For example, acrylic, PMMA or the like is employable. Thereception prism lens 171 is provided with boss pins 174 that areintegrally formed in the injection molding stage as a positioning meansfor the second injection mold in a portion that has no relation to theoptics. Moreover, by providing a satin finish to the surfaces 175 and176 of the reception prism lens 171, which do not make any opticalcontribution so that the unnecessary light emission and reflection ofthe emission light from the optical fiber are restrained.

FIG. 21A is a front view of a light emitting/receiving unit in which atransmission prism lens 182 and a reception prism lens 183 are inserted.FIG. 21B is a sectional view taken along line XXIb—XXIb of FIG. 21A.FIG. 21C is a side view of the light emitting/receiving unit. FIG. 21Dis a rear view of the light emitting/receiving unit.

As shown in FIGS. 21A through 21D, the transmission prism lens 182 andthe reception prism lens 183 are fixed in positions by inserting theboss pins 184 and 185 as a positioning means into the boss pin holes 142and 143 (shown in FIG. 18A) formed in the secondary injection moldingprocess for integrating or uniting the light-receiving and -emittingdevices.

It is possible that the transmission prism lens 161 and/or the receptionprism lens 171 falls off the assembly during the subsequentmanufacturing process steps if they are simply inserted in the secondaryinjection molded product. Therefore, lens fixing portions 195 are formedby tertiary injection resin molding to fix the lenses.

Further, in the lens fixing portion 195, pins 186 and 187 employed as apositioning means with respect to a jack section 202 (shown in FIG. 22A)described later are provided in two places by integral molding. The pins186 and 187 have different pin diameters in order to prevent theinsertion thereof in the wrong directions with regard to thetransmission side and the reception side when positioned and fixed withrespect to the jack section 202. Moreover, since mere press-fittinginvolves a risk of detachment of the jack section 202 from the lightemitting/receiving unit, the jack section 202 is provided with hooks 205(shown in FIG. 22A), and the light emitting/receiving unit 201 that hasundergone the tertiary injection resin molding is provided with grooveportions 194 to receive the hooks 205. The hooks 205 of the jack section202 and the groove portions 194 of the light emitting/receiving unit 201constitute an anti-detachment means. In the tertiary injection resinmolding stage, by carrying out the tertiary injection resin molding byperforming positioning on the basis of the pin holes 188 and 189 of thelead frames together with the light-emitting device 190 and thelight-receiving device 191 as in the secondary injection resin moldingstage, it is possible to improve the positioning accuracy of thepositioning pins 186 and 187 with respect to the light-emitting device190, light-receiving device 191 and lenses 192 and 193, which areintegrally molded by transfer molding, the prism lenses 182 and 183 fortransmission and reception, and the jack section 202.

FIG. 22A is a side view of the jack section 202. FIG. 22B is a side viewof a partition plate unit 221. FIG. 22C is a side view of a lightemitting/receiving unit 201. FIG. 22D is a view of the jack section 202of FIG. 22A as viewed from the lower side.

As shown in FIGS. 22A through 22D, the jack section 202, the partitionplate unit 221 and the light emitting/receiving unit 201 are assembledtogether through positioning by inserting the pins 186 and 187 of thelight emitting/receiving unit 201 formed by the tertiary injection resinmolding into pin holes 208 provided in the jack section 202. The jacksection 202 has a plug insertion hole (indicated by 24 in FIG. 3) and anengagement retaining portion for enabling the attaching and detaching ofan optical fiber cable (not shown) to which an optical plug is attached.This engagement retaining portion is designed to detachably retain theoptical plug inserted in the plug insertion hole in the prescribedposition of the jack section 202 by holding the optical plug by aconstricted portion (242 in FIG. 29) by means of a leaf spring or thelike (209 in FIG. 22). Moreover, as described above, since merepress-fitting involves a risk of detachment of the lightemitting/receiving unit from the jack section 202, the jack section 202is provided with hooks 205, 205, and the light emitting/receiving unit201 that has undergone the tertiary injection resin molding is providedwith groove portions 194 on both sides to receive the hooks 205, 205 tothereby prevent the detachment of the jack in the pulling direction. Thepartition plate unit 221 for separating the optical path of thetransmission signal light from the optical path of the reception signallight is held between the jack section 202 and the lightemitting/receiving unit 201. The partition plate unit 221 is constructedso as to be movable in the lengthwise direction of the optical fiber byvirtue of a partition plate unit retaining portion 215 provided at thejack section 202 and a spring 212 as a spring means.

FIG. 24 shows a flowchart for explaining the manufacturing method forthe partition plate unit. This partition plate unit is manufactured byintegrating the partition plate 211 with resin molded piece 213 forguiding the optical plug by insert molding in step S41 and thenpress-fitting the spring 212. The spring 212 may be integrated with theresin molded piece 213 by insert molding.

FIG. 23 shows a sectional view of an optical transmitter-receiver modulein a state in which an optical plug 240 is inserted in a plug insertionhole 227. As shown in FIG. 23, the partition plate unit 221 is providedwith a partition plate 211, which is positioned between a light-emittingdevice 222 and a light-receiving device 223 and between a transmissionprism lens 224 and a reception prism lens 225, and an engagement portion214 to which one end of the partition plate 211 is fixed. A partitionplate unit retaining portion 215 for retaining the partition plate unit221 movably in the direction of the optical axis of the optical fiber isprovided on the jack section 202 side of the partition plate unit 221.

FIG. 25 is a side view of the partition plate unit 221. FIG. 26 is afront view of the partition plate unit 221. FIG. 27 is a side view ofthe partition plate unit 221 of FIG. 26 seen from the right-hand side.FIG. 28 is a sectional view taken along line XXVIII—XXVIII of FIG. 26.

As is clearly depicted in the sectional view of the partition plate unit221 shown in FIG. 28, the engagement portion 214 has a generallytruncated cone-shaped hole 216 at the center to smoothly house the frontend of the optical plug 240 (shown in FIG. 23). The engagement portion214 also has an annular projection 217 that projects inwardly in theradial direction at the bottom of this hole 216. This annular projection217 has a thickness smaller than 0.4 mm (0<×<0.4 mm). The thickness ofthe annular projection 217 corresponds to an interval between the frontend of the optical plug 240 and a surface 218 (located on the sideopposite to the hole 216) of the partition plate 211. The partitionplate 211 is constructed of a phosphor bronze plate or a stainless steelplate of a thickness of about 50 μm and is fixed to the engagementportion 214 at the bottom portion of the hole 216 by insert molding. Thesurface 218 (located on the side opposite to the hole 216) of thepartition plate 211 is coated with a photoabsorption material (blackpaint containing carbon or the like), which forms a photoabsorptionlayer. Moreover, as is clearly depicted in the enlarged side view of thepartition plate unit 221 shown in FIG. 25 and the front view of thepartition plate unit 221 shown in FIG. 26, the leaf spring 212, which isconstructed of a phosphor bronze plate, a stainless steel plate or aberyllium copper, is mounted to the engagement portion 214 in two places(on the upper left side and the lower right side of FIG. 26) by insertmolding or press-fitting. The spring 212 is always brought in contactwith the light emitting/receiving unit 201 (shown in FIG. 23).Therefore, the engagement portion 214 is always urged toward the pluginsertion hole 227 (shown in FIG. 23), i.e., toward the optical fiber bythe spring 212. In FIG. 23, the engagement portion 214 is slidably fitin a rectangular hole (not shown) provided at the partition plate unitretaining portion 215 of the jack section 202. Therefore, if a forcegreater than the force of the spring 212 is exerted on the engagementportion 214, then the engagement portion 214 and the partition plate 211fixed to the engagement portion 214 move in the direction opposite fromthe plug insertion hole 227 (i.e., toward the light-emitting/receivingunit 201).

The optical transmitter-receiver module of this embodiment constitutesan optical transmitter-receiver system together with the optical cableshown in FIG. 29. This optical cable has optical plugs 240 at theopposite end portions (only one end portion is shown in FIG. 29), and anoptical fiber is inserted in the optical plugs 240. As is apparent fromFIG. 29, this optical plug 240 is provided with no anti-rotationmechanism and is therefore rotatable. An optical fiber end surface 241 aat the front end of the optical plug 240 projects from the plug(ferrule) end, and its outside portion in the radial direction coverspart of the plug end surface 240 a (see FIG. 30). The optical fiber endsurface 241 a is a curved surface rotationally symmetrical relative tothe optical axis of the optical fiber and is a convex surface. A flux ofreflection light from the curved surface is expanded and thereforeabsorbed into the cladding of the fiber when propagating through thefiber. Consequently, the reflection light going out of the fiber becomesreduced in comparison with an optical fiber that has a flat end surface.

FIG. 30 is a sectional view showing a state in which the front end ofthe optical plug 240 is fit in the hole 216 of the engagement portion214 of the partition plate unit 221.

As is clearly depicted in FIG. 30, when the optical plug 240 is put inthe optical transmitter-receiver module through the plug insertion hole227, the front end of the optical plug 240 is fit in the hole 216 of theengagement portion 214 of the partition plate unit 221, and a portion240 b that belongs to the plug end surface 240 a and is not covered withthe fiber end surface comes into contact with a surface (engagementsurface) 217 a of the annular projection 217 of the engagement portion214. As a result, the relative position of the front end of the opticalfiber 241 to the partition plate 211 is determined. At this time, a gapG corresponding to the thickness of the annular projection 217 of theengagement portion 214 is defined between the plug end surface 240 a(hence the outer edge of the optical fiber end surface 241 a) and theopposite surface 211 a of the partition plate 211. Since the opticalfiber end surface 241 a is made convex, the gap between the opticalfiber end surface 241 a and the opposite surface 211 a of the partitionplate 211 decreases as going towards the center of the fiber. However,due to the presence of the annular projection 217 that is projectinginward in the radial direction, the optical fiber end surface does nottouch the opposite surface of the partition plate. The dimension of thisgap G, which depends on the structure of the optical system, shouldpreferably have a value smaller than 0.4 mm (0 mm<G<0.4 mm) and be assmall as possible. In this embodiment, the gap G is set at about 0.3 mm.It was experimentally confirmed that the bit error rate (BER) could be10⁻¹² when the gap G was about 0.3 mm, and the full-duplex communicationsystem can sufficiently be provided.

As is obvious from the above, the annular projection 217 has a thicknessgreater than the amount of projection of the convex surface of theoptical fiber 241 from the optical plug end surface 240 b. Moreover, theopposite surface 211 a (facing the optical fiber end surface 241 a) ofthe partition plate 211 has a linear shape such that no gap is definedbetween an opposite surface 214 a (located on the side opposite from thesurface 217 a to be engaged with the optical plug 240) of theplastic-molded engagement portion 214 and the opposite surface 211 a ofthe partition plate 211.

The engagement portion 214 of the partition plate unit 221 is urgedtoward the plug insertion hole 227 (shown in FIG. 23), i.e., toward theoptical plug 240, by the spring 212. Therefore, the engagement surface217 a is always pressed against the plug end surface 240 a with a minuteforce. Moreover, the optical fiber end surface 241 a is a curved surfacerotationally symmetrical relative to the optical axis of the opticalfiber 241. Therefore, even if the optical plug 240 is rotated, the shapeof the optical fiber end surface 241 a does not change with respect tothe opposite surface 211 a of the partition plate 211, and the gap G iskept constant.

The optical plug 240 including the optical fiber 241 has a variation inlength due to the manufacturing process. Therefore, if the position ofthe partition plate 211 is fixed by fixing the partition plate unit 221to the jack section 202 (shown in FIG. 23) or by another means, then thegap between the optical fiber end surface 241 a and the opposite surface211 a of the partition plate 211 may become greater than is set,depending on the length of the optical plug 240. If the optical plug 240is a round type plug according to the EIAJ-RC5720B standard, then thelength of the plug may vary between 14.7 and 15 mm due to the variationsin the manufacturing process. If the gap is set at 0.2 mm and theposition of the partition plate 211 is fixed in conformity to thelongest optical plug 240, then there may occur a gap of 0.5 mm dependingon the plug. However, in the optical transmitter-receiver module of thisembodiment, the initial position of the partition plate unit 221 (morespecifically, of the engagement portion 214) is set at a position thatcan cope with the length of the possible shortest optical plug 240, andthe partition plate unit 221 is made movable in the lengthwise directionof the optical fiber 241 with the engagement portion 214 pressed againstthe plug end surface 240 b by the minute force of the spring 212.Therefore, whatever length the optical plug 240 inserted has, theinterval of the aforementioned gap can be kept constant.

Moreover, since the plug end surface 240 b in contact with theengagement surface 217 a slides on the latter by the rotation of theoptical plug 240, it is desirable to use for the engagement surface 217a a material of a small sliding friction coefficient and excellentabrasion resistance, such as fluoroplastic and ultrahigh molecularweight polyethylene.

In the assembly 1 of the structure in which the partition plate unit 221is held between the light emitting/receiving unit 201 and the jacksection 202, a surface 211 b of the partition plate 211, which islocated on the side opposite from the opposite surface 211 a facing theoptical fiber 241, is to be inserted into the partition plate guidinggroove portion 228 (shown in FIG. 23) of the light emitting/receivingunit 201. As shown in FIG. 23, since the light-emitting device 222 islocated farther apart from the optical fiber end surface in thedirection of the optical axis of the optical fiber 241 than thelight-receiving device 223 is, the partition plate 211 is made in alength such that the partition plate 211 extends beyond the bottomportion of the lens 222 a of the light-emitting device 222. With thisarrangement, light from the light-emitting device 222 that is notincident on the transmission prism lens 224, is prevented from enter thelight-receiving device 223 directly or after being reflected on thereception prism lens 225.

The operation of the optical transmitter-receiver system of thisembodiment will be described next.

FIG. 5 shows a sectional view of the essential part of one side of theoptical transmitter-receiver system where the optical plugs 240 at bothends of the optical cable are each inserted in the respective opticaltransmitter-receiver modules. Once a transmission signal (electricalsignal) is inputted from the outside of the optical transmitter-receivermodule 20 via the input/output terminal 25 (shown in FIG. 4), an LED 514that serves as a light-emitting device is driven by a transmission driveelectric circuit board 509 on which a transmission drive IC 512 ismounted, so that transmission signal light rays (optical signal) areemitted from the LED 514. The transmission signal light rays aresubstantially collimated by a transmission lens 516 formed at thesurface of the light-emitting device 501, and then enter a transmissionprism lens 503, by which the light rays deflect the optical path andenter the optical fiber 241. At this time, transmission light raysreflected from an end surface, of the optical fiber 241, near to theoptical transmission and reception module (hereinafter referred to as an“optical fiber end surface on the near side”) pass through the gap Gbetween the partition plate 211 and the optical fiber end (shown in FIG.30) and enter the light-receiving device 502. At this time, since thegap G has a small dimension of 0.3 mm, the incident light issufficiently small in light quantity.

The transmission light rays which have been transmitted through theoptical fiber are partly reflected by an end surface, of the opticalfiber 241, far from the optical transmission and reception module(hereinafter referred to as an “optical fiber end surface on the farside”). However, since the optical fiber end surface on the far side isa convex surface, a flux of reflection light rays is expanded andabsorbed into the cladding while propagating through the optical fiber241. As a result, little reflection light goes out of the optical fiberend surface 241 a on the near side.

On the other hand, the transmission signal light discharged from theoptical fiber end surface on the far side is incident on the opticaltransmitter-receiver module of the other party of communication.Assuming that the optical transmitter-receiver module of the other partyof communication has the same construction (for which the same referencenumerals will be used in the following description), the transmissionsignal light first reaches the opposite surface 211 a (shown in FIG. 30)of the partition plate 211. However, since this opposite surface 211 ais coated with a photoabsorption material (black paint containing carbonor the like), no reflection light is generated here.

Subsequently, the transmission signal light incident on the receptionprism lens 504 has its optical path changed and is condensed by areception lens 517 formed on the surface of the light-receiving device502 to enter a PD 515 that serves as a light-receiving device.

The incident light is partially reflected on this PD 515. However,because the incident light was obliquely incident on the PD 515, thelight is reflected in the opposite oblique direction and does not returnto the transmission prism lens 504. Subsequently, the light incident onthe PD 515 is photoelectrically converted into an electric signal,amplified by a reception amplification electric circuit board 510 onwhich an amplification IC 513 is mounted, and taken out as a receptionsignal through the external input/output terminal 25 (shown in FIG. 4)to the outside of the optical transmitter-receiver module.

This optical transmitter-receiver system suppresses the electricalcrosstalk by using the shield plates and suppresses the opticalcrosstalk by using the partition plate unit 506 that has the partitionplate opposite to the optical fiber end surface with interposition of asmall gap. Therefore, optical transmission by the full-duplexcommunication scheme is achieved. Moreover, because the gap is providedbetween the partition plate and the optical fiber end surface, no damagedue to the rotation of the optical plug 240 occurs on the optical fiberend surface and the partition plate.

The processes of assembling the light-emitting element drive electriccircuit board, the light-receiving element amplification electriccircuit board and the armor shield will be described next.

FIG. 31 is a sectional view of the optical transmitter-receiver modulewhere the optical plug 240 is inserted in the jack section 202. In FIG.31, lead terminals 251 of the light-emitting device 222 of the lightemitting/receiving unit 201 are inserted into connection holes 253provided at the light-emitting element drive electric circuit board 252,and electrically connected by soldering. Likewise, lead terminals 254 ofthe light-receiving device 223 of the light emitting/receiving unit 201are inserted into connection holes 256 provided at the light-receivingelement amplification electric circuit board 255, and electricallyconnected by soldering.

FIG. 32A is a plan view of the light-emitting element drive circuitboard 252. FIG. 32B is a plan view of the light-receiving elementamplification electric circuit board 255. As shown in FIGS. 32A and 32B,the light-emitting element drive circuit board 252, on which thelight-emitting device driver IC 257 is mounted, is generally flat in itsheight direction. The light-receiving element amplification electriccircuit board 255, on which the reception amplification IC 258 ismounted, is also generally flat in its height direction. Thelight-emitting element drive circuit board 252 and the light-receivingelement amplification electric circuit board 255 are assembled so thattheir rear surfaces oppose to each other with the interposition of theassembly 1 (combination of three parts of the light emitting/receivingunit 201, the partition plate unit 221 and the jack section 202)therebetween, centering on the optical plug 240. An assembly 2 isthereby produced. More specifically, the light-emitting element drivecircuit board 252 and the light-receiving element amplification electriccircuit board 255 are arranged so that the longer sides of each boardare parallel to the axis of the plug 240 and the shorter sides extendalong the direction of height of the jack section 202. As describedabove, the light-emitting element drive circuit board 252 and thelight-receiving element amplification electric circuit board 255 areeach arranged in an upright posture between the light-emitting device222 (shown in FIG. 31) and the light-receiving device 223 and the pluginsertion hole side of the jack section 202 so that the area ofprojection becomes minimized, i.e., so that the height direction of theflat light-emitting element drive circuit board 252 and thelight-receiving element amplification electric circuit board 255corresponds to the widthwise direction of the jack section 202. Withthis arrangement, the length of the optical transmitter-receiver module(i.e., the size in the axial direction of the optical plug 240) and thewidth of the optical transmitter-receiver module (i.e., the size in thedirection perpendicular to the axis of the optical plug 240) arereduced, by which the downsizing of the optical transmitter-receivermodule is achieved. The light-emitting element drive circuit board 252and the light-receiving element amplification electric circuit board 255are provided with boss pin holes 261 and 262 in which the board fixingand positioning boss pins 259 and 260 (shown in FIG. 31) provided forthe jack section 202 are respectively inserted. The positioning andfixation of the light-emitting element drive circuit board 252 isachieved by first inserting the lead terminals 251 (shown in FIG. 31) ofthe light-emitting device 222 into the corresponding holes 253 providedat one end of the board and then soldering, and then inserting the boardfixing and positioning boss pin 259 (shown in FIG. 31) of the jacksection 202 into the boss pin hole 261 provided at the other end of theboard. Furthermore, the positioning and fixation of the light-receivingelement-amplification electric circuit board 255 is achieved byinserting the lead terminals 254 (shown in FIG. 31) of thelight-receiving device 223 into the holes 256 provided at one end of theboard and then soldering, and further inserting the board fixing andpositioning boss pin 260 of the jack section 202 into the boss pin hole262 provided at the other end of the board.

Then, referring to FIG. 31, an armor shield plate 263 is mounted on anassembly 2 (the light emitting/receiving unit provided with thelight-receiving and -emitting boards and the jack) in order neither toreceive the influence of external noises nor to let noises go outside.The armor shield plate 263 is fixed by inserting engagement portions ofthe armor shield plate 263 into the corresponding shield plate retainingrectangular holes 26 (shown in FIG. 3) provided in four places of thejack section 202 and then soldering the armor shield plate onto apattern 264 and 265 (shown in FIG. 32) provided on the light-emittingelement drive circuit board 252 and the light-receiving elementamplification electric circuit board 255 respectively to serve as agrounding portion. By grounding the soldering portions (patterns 264 and265) of the light-emitting element drive circuit board 252 and thelight-receiving element amplification electric circuit board 255, thearmor shield plate 263 can be grounded, obviating the need forseparately providing a grounding terminal to the armor shield plate 263.Although this embodiment employs the armor shield plate 263 of which thelight-emitting side 263 a and the light-receiving side 263 b areintegrated with each other, it is acceptable to employ an armor shieldplate divided into two parts. It is also acceptable to separatelyprovide a grounding terminal for the armor shield plate 263.

The boss pin hole 261 that serves as a first hole provided at one end ofthe light-emitting element drive circuit board 252, the board fixing andpositioning boss pin 259 that serves as a projection provided for thejack section 202, the connection holes 253 that serve as second holesprovided at the opposite end of the light-emitting element drive circuitboard 252, and the lead terminals 251 of the light emitting/receivingunit 201, all together, constitute a board positioning means. Moreover,the boss pin hole 262 that serves as a first hole provided at one end ofthe light-receiving element amplification electric circuit board 255,the board fixing and positioning boss pin 260 that serves as aprojection provided at the jack section 202, the connection holes 256that serve as second holes provided at the opposite end of thelight-receiving element amplification electric circuit board 255, andthe lead terminals 254 of the light emitting/receiving unit 201, alltogether, constitute a board positioning means.

In the present embodiment, the positioning and fixation are performed byinserting the projections provided at the transmission prism lens andthe reception prism lens into the holes provided at the lightemitting/receiving unit. However, it is acceptable to perform thepositioning and fixation by providing holes at the transmission prismlens and the reception prism lens, providing projections at the opticallight emitting/receiving unit and inserting the projections of theoptical light emitting/receiving unit into the holes of the prismlenses.

Furthermore, in the present embodiment, the light emitting/receivingunit is prevented from detaching from the jack section by providinghooks at the jack section, providing grooves at the lightemitting/receiving unit and fitting the hooks of the jack section in thegrooves of the light emitting/receiving unit. However, it is acceptableto prevent the light emitting/receiving unit from the detachment byproviding a groove at the jack section, providing a hook at the lightemitting/receiving unit and fitting the hook of the lightemitting/receiving unit into the groove of the jack section.

The optical transmitter-receiver module of this invention is applicableto electronic equipment such as a digital TV set, a digital BS tuner, aCS tuner, a DVD player, a SuperAudio CD player, an AV amplifier, anaudio device, a personal computer, personal computer peripherals, amobile phone, a PDA (personal data assistant) and the like.

For example, as shown in FIG. 33, it is possible to serially connect,using a single-core optical fiber cable, a personal computer 601, atelevision set 602, a DVD player 603, a tuner 604 and a home theatersystem 605, these devices employing the optical module of the presentinvention, to thereby construct an optical transmitter-receiver systemfor performing bidirectional optical transmission between the devices bythe full-duplex communication scheme.

Referring to FIG. 34, if an audio system 701 and a personal computer 702are connected with each other via an electric communication interface ofIEEE1394 or the like, then noises generated from the personal computer702 exert bad influence on the audio system 701. To avoid this, theaudio system 701 may be connected with a personal computer 704 via aphotoelectric converter 703. In this case, an opticaltransmitter-receiver system for performing bidirectional opticaltransmission by the full-duplex communication scheme using the opticaltransmitter-receiver module of this invention may be realized byconnecting the personal computer 704 with the photoelectric converter703 via an electric communication interface and connecting thephotoelectric converter 703 with the audio system 701 via a single-coreoptical fiber cable.

Although the LED is employed as a light-emitting element in theembodiment, it is acceptable to employ a semiconductor laser element asthe light-emitting element.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An optical transmitter-receiver module having alight-emitting element for emitting transmission signal light and alight-receiving element for receiving reception signal light, saidmodule being able to perform both transmission of the transmissionsignal light and reception of the reception signal light by means of asingle-core optical fiber, said module comprising: a jack section fordetachably holding an optical plug provided at an end portion of theoptical fiber; a light emitting/receiving unit having the light-emittingelement and light-receiving element positioned and fixed in place andmolded in one piece; and a light-tight partition plate unit forseparating an optical path of the transmission signal light and anoptical path of the reception signal light from each other, saidlight-tight partition plate being arranged so as to be held between thejack section and the light emitting/receiving unit, the light-tightpartition plate unit having spring means for urging this unit toward theoptical fiber.
 2. The optical transmitter-receiver module as claimed inclaim 1, wherein the partition plate unit has a partition plate forseparating an optical path of the transmission signal light and anoptical path of the reception signal light from each other, aresin-molded piece having an engagement surface with which an endsurface of the optical plug comes in contact when inserted in the jacksection, and the spring means urging the engagement surface of theresin-molded piece toward the optical plug, and the module furthercomprises a retaining portion for retaining the partition plate unitmovably in a direction of optical axis of the optical fiber.
 3. Theoptical transmitter-receiver module as claimed in claim 2, wherein thespring means of the partition plate unit are provided in at least twoplaces located on a plane approximately perpendicular to the opticalaxis of the fiber and on a diagonal line of the resin molding.
 4. Theoptical transmitter-receiver module as claimed in claim 2, wherein thepartition plate and resin-molded piece of the partition plate unit areformed into one piece by insert molding.
 5. The opticaltransmitter-receiver module as claimed in claim 2, wherein the partitionplate of the partition plate unit has a planar opposed surface thatfaces an end surface of the optical fiber with a gap therebetween whenthe optical plug is placed in position within the module.
 6. The opticaltransmitter-receiver module as claimed in claim 5, wherein an opticalabsorption layer is provided on the opposite surface of the partitionplate.
 7. The optical transmitter-receiver module as claimed in claim 2,wherein said engagement surface of the resin-molded piece comes incontact with a peripheral edge portion of the end surface of the opticalplug.
 8. The optical transmitter-receiver module as claimed in claim 2,wherein the partition plate is sized such that a distance in a directionof optical axis from said end surface of the optical fiber to an endopposite from the optical fiber of the partition plate is greater thandistances in a direction of optical axis from said end surface of theoptical fiber to each of a bottom of a transmission lens provided onemission side of the light-emitting element and a bottom of a receptionlens provided on incident side of the light-receiving element.
 9. Anelectronic device employing the optical transmitter-receiver module asclaimed in claim 1.